Introduction:
Pendred syndrome is named after Vaughan Pendred, the physician who discovered this syndrome. This syndrome affects hearing at an early age, and sometimes the thyroid gland is also affected. The thyroid gland is present at the throat near the trachea and is shaped like a butterfly. This syndrome is mainly seen in children, with severe profound hearing loss visible at birth.
What Is Pendred Syndrome?
It is a syndrome that leads to hearing loss and goiter (a thyroid condition). While growing up, normal growth and development of the thyroid are essential. It mainly affects children, and children with this condition may have complete hearing loss by the age of three. In most cases, hearing loss caused due to inner ear (sensorineural hearing loss) is seen. Sensorineural hearing loss is very common and occurs when the inner ear is damaged. Some affected individuals have difficulty balancing and orientation due to vestibular system dysfunction when the inner ear is damaged. In addition, almost all cases have bilateral hearing loss (loss of hearing in both ears). Through research, it has been found that 40 to 50 percent of Pendred syndrome cases in the United States are due to genetics, and the other 40 to 50 percent of the cases are due to environmental causes.
What Are the Other Names For Pendred Syndrome?
The various other names are as follows:
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Autosomal recessive sensorineural hearing impairment, enlarged vestibular aqueduct, and goiter.
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Deafness with goiter.
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Goiter-deafness syndrome.
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Pendred's syndrome.
What Is the Prevalance of Pendred Syndrome?
It is unknown how common Pendred syndrome is. However, according to research, it only accounts for seven to eight percent of hearing loss that is congenital, or present from birth.
What Are the Causes of Pendred Syndrome?
The leading cause of Pendred syndrome is a genetic mutation. Mutation in the SLC26A4 (solute carrier family 26 member 4) gene is responsible for the same. The SLC26A4 gene provides instructions to make the protein named pendrin. The pendrin protein transports the ions (negatively charged), such as chloride and iodide, around the cell membrane. Pendrin is produced in different tissues and organs of the body, like the inner ear and the thyroid gland. For example, in the inner ear, pendrin controls the ions balance, and it is essential during the bony structure formation around the vestibular aqueduct (a bony canal connecting the inner ear and inside of the skull) and the cochlea (snail-shaped that processes sound). In some of the SLC26A4 gene mutations, single protein blocks (amino acids) are changed, while some other mutations delete a small amount of the DNA (deoxyribonucleic acid) in the gene. These changes impair the pendrin activity and cause disruption in the transportation of the protein.
Now in the thyroid gland, these disrupted ions stop the iodide ions from being transported to the thyroid hormone. This is why the thyroid tissue enlarges and forms a goiter to compensate for the missing iodide ion.
The hearing loss is due to changes in the ion levels leading to loss of the sensory cells in the inner ear.
How Is Pendred Syndrome Inherited?
This disorder is inherited in an autosomal recessive manner, which means that both copies of the gene in each cell are mutated. One copy of the defective gene is carried by each parent of a person with an autosomal recessive disorder, although they normally do not exhibit the disease's signs and symptoms.
What Are the Symptoms of Penderd Syndrome?
The most common symptoms of this condition include:
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Swelling around the base of the neck (goiter).
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Hearing loss.
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Malformation of the inner ear or enlarged vestibular aqueduct.
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Speech impairment.
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Vertigo (spinning or dizzy sensation).
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Hypothyroidism (underactive thyroid gland).
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Difficulty balancing.
How Can Penderd Syndrome Be Diagnosed?
Some of the methods through which Penderd syndrome can be diagnosed include:
Magnetic Resonance Imaging (MRI) Scan - An MRI scan of the ear helps diagnose the cochlea's shape and structure. A healthcare professional will ask the patient to lie down on the bed of the machine. Once the patient is settled, the expert will operate the machine in a different chamber. The machine will take several scans, which take around half an hour to complete.
Genetic Testing - It examines the DNA, a database that carries instructions for the body’s functions. It is always informed before genetic testing that, in some cases, the negative result does not confirm the diagnosis, and the test can be performed again. The blood test is done by a healthcare expert who takes the blood from the arm’s vein, and the sample is sent to the laboratory for further testing. This test will help the family member denote if they have a risk of having or passing on Pendred syndrome.
How Is Penderd Syndrome Managed?
Some of the treatment options include:
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Genetic counseling helps the patient and family to understand the condition. The genetic counselor will detail how likely a family member has Pendred syndrome. This counseling especially helps a woman who is planning to or is pregnant.
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In people with swollen thyroid glands, thyroid supplements can be given.
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To reduce the progression of hearing loss, a doctor may give protective gear to the head to avoid injury.
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Hearing aids can be given to children to listen better and improve social skills. Early treatment or therapy to learn sign language is also beneficial.
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Agents and situations to avoid: According to some research, abrupt drops in hearing may be connected to sharp increases in intracranial pressure. The safety of weightlifting and contact sports should therefore be discussed with a doctor or other healthcare professional before participating.
Conclusion:
It is a genetic condition that can cause hearing loss and goiter. It mostly affects children and is caused due to a mutation of gene SLC26A4 (solute carrier family 26 member 4). The symptoms are visible from an early age and, if diagnosed early, can help avoid complications. Genetic and MRI tests confirm and give a clearer view of the condition. Hearing aids and genetic counseling can help better understand and recover from this condition.
